tracer

README

tracer

Annotate a golang http request to trace time taken at various steps.

Heavily inspired by https://github.com/davecheney/httpstat :)

Note: Just as any other instrumentation tool, don't keep this running in production forever without understanding the cost. If you are doing a lot of requests, this might have some (tiny) impact.

Usage:

import "github.com/urjitbhatia/tracer"

req, _ := http.NewRequest(http.MethodGet, "http://golang.org", body)
req, tr = tracer.AsTraceableReq(req)
// ...
resp, err := client.Do(req)
if err != nil {
    log.Fatalf("failed to read response: %v", err)
}
body := readResponseBody(req, resp)
resp.Body.Close()
// Important to call this to calculate total time taken, otherwise it will be negative
tr.Finish()

// ..
log.Printlf("Tracer stats: %v", tr)

2018/08/10 06:23:48 Tracer stats: {"total":1.917301,"dnsLookup":0.526224, "tcpDialed":0.170330, "connSetup":0.684807, "preTransfer":1.211031, "ttfb":1.917138, "serverProcessing":0.706107, "contentTransfer":0.000162}

If you see bugs, please feel free to post issues.

Documentation

Index

• type Tracer
  • func AsTraceableReq(req *http.Request) (*http.Request, *Tracer)
  • func (t *Tracer) ConnSetup() time.Duration
  • func (t *Tracer) ContentTransfer() time.Duration
  • func (t *Tracer) DNSLookup() time.Duration
  • func (t *Tracer) Finish()
  • func (t *Tracer) PreTransfer() time.Duration
  • func (t *Tracer) ServerProcessing() time.Duration
  • func (t *Tracer) String() string
  • func (t *Tracer) TCPDialed() time.Duration
  • func (t *Tracer) TimeToFirstByte() time.Duration
  • func (t *Tracer) Total() time.Duration

Types

type Tracer

type Tracer struct {
	// contains filtered or unexported fields
}

Tracer records timings for an http request

func AsTraceableReq

func AsTraceableReq(req *http.Request) (*http.Request, *Tracer)

AsTraceableReq wraps a given *http.Request with tracing timers and returns the wrapped request Use the returned Tracer value to query for various timing values that were recorded

func (*Tracer) ConnSetup

func (t *Tracer) ConnSetup() time.Duration

ConnSetup returns time taken to fully create a connection that is ready to perform an http request

func (*Tracer) ContentTransfer

func (t *Tracer) ContentTransfer() time.Duration

ContentTransfer returns time taken from first byte till body is fully read

func (*Tracer) DNSLookup

func (t *Tracer) DNSLookup() time.Duration

DNSLookup returns dns lookup time taken

func (*Tracer) Finish

func (t *Tracer) Finish()

Finish should be called as soon as a request body is read This method is important to calculate the total time taken

func (*Tracer) PreTransfer

func (t *Tracer) PreTransfer() time.Duration

PreTransfer returns total time taken to setup everything before the server has a connection ready to go.

func (*Tracer) ServerProcessing

func (t *Tracer) ServerProcessing() time.Duration

ServerProcessing returns time taken by the server to receive the request and start replying (TimeToFirstByte since connection setup)

func (*Tracer) String

func (t *Tracer) String() string

String representation

func (*Tracer) TCPDialed

func (t *Tracer) TCPDialed() time.Duration

TCPDialed returns time taken to dial the connection over tcp

func (*Tracer) TimeToFirstByte

func (t *Tracer) TimeToFirstByte() time.Duration

TimeToFirstByte returns time since start till FirstResponse Byte

func (*Tracer) Total

func (t *Tracer) Total() time.Duration

Total returns time take from very start to when tracer.Finish() was called